System color 'canvas' cannot be set or read

[Дилян Палаузов]

The way to obtain the default background color set by the user, is to call

function getDefaultBackgroundColor() {
  let div = document.createElement("div");
  div.style.backgroundColor = "canvas";
  document.documentElement.appendChild(div);
  let color = getComputedStyle(div).backgroundColor;
  div.remove();
  return color;
}

This does not work with WebKitGTK 2.28.1/Epiphany 3.36.4.  In particular it allows setting custom CSS, and body.background-color in it, but it is unclear how to use the Canvas keyword as calor there.

• How to configure WebKit to change the default canvas system colour, in terms of https://www.w3.org/TR/css-color-4/#css-system-colors
• Please make the snippet above work.

See also https://bugzilla.mozilla.org/show_bug.cgi?id=1666127 and https://gitlab.gnome.org/GNOME/epiphany/-/issues/1344

[Emilio Cobos Álvarez (:emilio)]

Ideally WebKit would support color: canvas and would allow users to change it, otherwise you need to use user stylesheets which don't reliably work.

[Radar WebKit Bug Importer]

<rdar://problem/69397317>